This invention relates generally to an apparatus for writing and/or reading information on disklike record media such as flexible magnetic disks, and more specifically to such an apparatus of the kind having a drive pin resiliently supported in an eccentric position on a turntable. The drive pin is engageable in an eccentric opening in the record medium for imparting the rotation of the turntable thereto. Still more specifically, the invention deals with an improved support mechanism for the drive pin of such a rotating disk data storage apparatus.
A flexible magnetic disk having an eccentric slot to be engaged by a drive pin is disclosed in U.S. Pat. No. 4,758,915 to Sakaguchi. This known magnetic disk has a diameter of three and a half inches and is rotatably housed in a generally flat, boxlike envelope of relatively rigid plastic material to make up a disk cassette. The magnetic disk has a rigid hub of magnetic material attached centrally thereto. The hub has a central opening of square shape and an eccentric opening of rectangular shape.
When a disk cassette is positioned in a disk drive, the magnetic disk has its central hub placed on a turntable which has a much smaller diameter than that of the disk. The turntable has a permanent magnet mounted thereon for attracting the disk hub. A spindle is disposed centrally on the turntable and engages in a central opening in the disk hub for centering the disk on the turntable. A drive pin is disposed eccentrically on the turntable for engaging the eccentric opening or slot in the disk hub and imparting the rotation of the turntable to the magnetic disk.
The drive pin must be resiliently supported on the turntable for both radial displacement parallel to the turntable and a displacement along an axis of the spindle. The radial and inward displacement of the drive pin is necessary for holding the disk in a proper position with respect to the turntable as the drive pin imparts the rotation of the turntable to the disk. The drive pin displacement parallel to the spindle axis is necessary to cause the drive pin to spring into the driving engagement position in the eccentric slot in the disk hub after the turntable starts rotation in sliding contact.
Conventionally, for resiliently supporting the drive pin, a planar spring was employed as disclosed in Sakaguchi U.S. Pat. No. 4,758,915, supra. A planar drive pin support spring is disposed parallel to the turntable and permits an easy displacement of the drive pin substantially parallel to the spindle axis. For a radial and inward displacement of the drive pin over the turntable, the planar drive pin support spring undergoes a torsional displacement which causes the drive pin to slant in the required direction.
This prior art device proved unsatisfactory as a current trend for disk drives is the reduction in their thickness or height. That is, the dimension in the axial direction of the spindle is reduced. This trend inherently demands the reduction of the space required for the deflection of the drive pin support spring along a substantially parallel axis of the spindle.
The space for deflection of the drive pin support spring needs to be smaller when the electric motor for driving the turntable is of the known rotor-outside-stator configuration. This type of motor has a rotor of annular shape coaxially secured to the periphery of the turntable for joint rotation therewith, and stator windings formed on a printed circuit board underlying the turntable. The space between the drive pin support spring and the stator windings is so small that the spring upon deflection easily hit the stator windings to cause damages.